The present invention is directed to a corrosion-inhibiting composition and to a method of protecting metallic surfaces from corrosion using the same, and more specifically corrosion inhibitors for coating compositions, and the coating compositions containing such corrosion inhibitors.
Metal surfaces can undergo very rapid corrosion, sometimes even within very short windows of exposure to certain conditions. Significant corrosion can occur in mere minutes or hours depending upon the conditions, and particularly when the metal surfaces are in contact with aqueous solutions, particularly acidic solutions, with highly ionic solutions, and even with hard water. This rapid corrosion is commonly referred to as “flash rust” in the case of ferrous metal surfaces, but is equally a problem with non-ferrous metal surfaces as well. The term “flash rust” as used below refers to the rapid corrosion whether the materials involved are ferrous or non-ferrous.
Not all flash rust is readily visible, yet the presence of any such corrosion can be harmful and can be generally detected upon more in-depth analysis. Flash rust and other forms of corrosion can be particularly problematic in the manufacture of metallic components for various uses when the components will come in contact with aqueous solutions during fabrication, assembly or subsequent testing or use.
There is an ongoing need to reduce, and if possible prevent, flash rust from occurring. There is also an ongoing need to reduce other types of corrosion so that surfaces and parts may last longer and not experience premature failures due to corrosion-related damage.
Commercially available corrosion inhibitors often have low water solubility, such as metallic sulfonates, pigment compositions containing heavy metal salts (e.g., zinc) of carboxylic acids, benzoates, nitrites and nitrates. In addition, flash rust inhibitors formed with nitrites and nitrates have limited use as long-term corrosion inhibitors in direct to metal applications as the toxicity of these corrosion inhibitors make them less attractive for commercial use.
In addition, while nitrites and nitrates mixed with amines are effective flash rust inhibitors, they can react to form N-nitrosamines, which are known carcinogens.
Consequently, a need exists for a corrosion inhibitor for coating compositions that provides early flash rusting protection, and which may also provide long-term corrosion protection. There is also a need for corrosion inhibitors that provide the desired performance in coating compositions while also being cost effective, free of heavy metals, free of nitrites, free of solvents, free of toxic and/or environmentally unfriendly materials, or any combination thereof. The corrosion inhibitors ideally would not absorb oil and could be added directly to coatings compositions, such that the coating composition provides early flash rusting protection and even long-term corrosion protection to the surface the coating is applied to. Or the CI could be made inside in-situ.
In light of the above discussion and problems being encountered, there is a continuing need for advancements in the relevant fields, including improved coating and methods for treating these and other metallic components to reduce flash rust or corrosion and also to deal with it if it occurs. The present invention is addressed to these needs.